class Cart < ApplicationRecord
  has_many :line_items, dependent:  :destroy


def add_product(product)
   current_item = line_items.find_by(product_id: product.id)
  if current_item
    current_item.quantity += 1
  else
    current_item = line_items.build(product_id: product.id)
  end
  current_item
end
  def total_price
    line_items.to_a.sum { |item| item.total_price}
  end
end